This invention pertains to the art of tapping conduits, pipes, or tube-like workpieces and, more particularly, to tapping an existing, pressurized conduit for connection with another conduit. The invention is particularly applicable to tapping a gas main and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may be advantageously employed in other related tapping environments and uses.
In providing natural gas to homes and businesses, gas mains are usually buried either under a street or adjacent the street for the purpose of conveying pressurized natural gas to various locations. When gas service is desired at a home or business, a service line is installed for interconnecting the building involved with the gas main. The service line is typically about one inch in diameter and will have a length that varies from a few feet to fifty feet or more.
With the advent of polymer or plastic pipe in the gas industry, tapping tees have changed dramatically and come into widespread use. A tapping tee incorporates a drill-like or cutting tool with a mounting collar for allowing the tee to be positioned at any desired location along the main. Typically, the tee is first attached to the main by using a split collar arrangement or, alternately, the tee may be fused to the main through use of a heating iron or the like. Thereafter, the cutting tool is advanced through the sidewall of the main, and is removed therefrom for opening a fluid passage between the gas main and tee assembly.
Heating irons for attaching a plastic saddle of a tee to a gas main have found widespread use. The heating iron typically has a curvature complementary to the curvature of the tee saddle and the external surface of the gas main to facilitate simultaneous heating of these two surfaces until the plastic at the saddle and the gas main softens. When sufficient softening has taken place, the heating iron is removed and the saddle of the tee is caused to be directly fused to the main. A principle drawback in use of heating irons is the fact that considerable operator skill and caution are required. If too much heat is applied, the main can simply collapse, producing considerable gas leakage requiring extensive repairs. If insufficient heat is applied, the saddle and gas main will not properly fuse together.
Split collars which are held together by interconnecting bolts also find wide use. More recently, however, a question about split collars has been raised by certain industry standard groups. This resides in the fact that code requirements call for placement of an internal stiffener or liner in a plastic tube or pipe when an external compressive force is to be exerted thereon. Thus, as a split collor or similar mounting clamp exerts a compressive force on the tube, the stiffener provides reinforcement and offers resistance to tube collapse with increased tightening of the split collar.
However, where it is desired to attach a tapping tee to a continuous, pressurized gas main, it is not feasible or practical to insert an internal metallic stiffener into the main before the tee is attached. The obvious advantage of a tapping tee is that it is not, in fact, necessary to actually sever the entire main in order to interconnect the tee. Rather, the tapping tee requires only that a hole be drilled into the main in order to provide for an escape of gas therefrom.
It has, therefore, been considered desirable to utilize the advantages of a split collar tapping tee but in a manner that overcomes the problems discussed above. The subject invention is deemed to meet these needs and others.